Interface study of spiro-ometad on passivated p-, n-, and n +-Si(111) for use in tandem perovskite/silicon solar cell devices.

摘要

The organic semiconductor 2,2',7,7'-tetrakis-(N,N-di- p-methoxyphenylamine)9,9'-spirobifluorene (Spiro-OMeTAD) contact properties are studied on p-, n-, and n+-type silicon. Spiro-OMeTAD is a solid state hole conductor that has notably been used in perovskite solar cells achieving 20.1% efficiency. In this work spiro-OMeTAD doped with 20 mol% bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) is investigated as a spin and drop cast film on p, n, and n+-Si(111) surfaces terminated with H and CH3. An ohmic like tunnel junction has been observed on CH3- terminated p-, n-, and n+-Si(111) and also H-terminated p and n+-Si(111). Rectifying contacts have been found on n type H-terminated silicon. Low contact resistances have been found when the doped hole transport material contacts n+-Si(CH3) which has been found to be as low as 0.622 O·cm2 +/- 0.439 O·cm2. Other types of methyl-terminated silicon have been found to have contact resistances of 22.92 kO·cm 2 -54.34 kO·cm2 for n-Si and 0.51 kO·cm 2 - 3.12 kO·cm2 on p-Si (111) surfaces. H-terminated data for n+-Si(111) has been found to be as low as 1.34 +/- 0.54 kO·cm 2 and 1.3 +/- 0.28 kO·cm2 for p-Si(111). A photo-responsive CH3NH3PbIxCl3-x perovskite solar cell was fabricated utilizing n+-Si(CH3) as an anode and a 20 mol% Li-TFSI doped spiro-OMeTAD which resulted in <1% photoconversion efficiency. The 'pre-doped' spiro(TFSI)2 dicationic salt was used as an alternative to the uncontrollable air doping method from a spin cast film resulting in a contact resistance of 12 - 201 O·cm2.